Toronto, Canada – By Greg Stutchbury
The world number one was never really put under sustained pressure by the 16th seed, who was making her first grand slam semi-final appearance, and secured a place in Saturday's final against Li's compatriot Zheng Jie or Belgian Justine Henin.
Rather than blasting winners from every angle, as she was forced to do in her quarter-final against Victoria Azarenka, Williams waited patiently for her opportunities and unleashed a winner or massive serve when required.
Williams held three match points, all saved by Li, in the 10th game of the second set, and another in the 12th before she sealed victory with her 12th ace. "I really should have won sooner, she played well. Every time I had match points she came up with a big serve or amazing shot," Williams told ESPN in a courtside interview.
"But I really wanted to finish it on my serve and put an exclamation point on it."
A small pocket of Australia's Chinese community held up signs reading "Li Na jia you!" -- meaning "Add Oil" or "C'mon!" -- and provided vocal support for Li, who came from a set down to upset Venus Williams in the quarter-finals Wednesday.
The younger Williams is mental tougher than her sister, however, and Thursday she also rediscovered her power game.
Prior to her quarter-final against Azarenka, Williams had not dropped a set or been broken in 31 service games in her four previous matches. Azarenka broke her five times.
Her dominant serve returned against Li, the Chinese winning just four receiving points in the first nine games.
Li, however, found her groove in the 10th game, pushing returns wide and forcing Williams to move off her baseline and, while the stubborn American fended off two break points, Li was able to draw level at 5-5.
Both held to send it into a tiebreak, with Williams winning four of the first five points to give her the cushion she required to take it 7-4.
The second set was a patient tactical battle, with each content to wait for their opportunities as the rallies progressed.
Li was required to dig deep on serve in the sixth game of the second set, although she never gave Williams a break point opportunity until the 10th game when the American held three match points.
The Chinese was at her scrambling best as she saved all three, then saved another while serving in the 12th, but Williams finally ended her resistance in the tiebreak in a touch over two hours.
(additional reporting by Ian Ransom)
(Editing by Nick Mulvenney)